Volume 6, Number 4—August 2000
Research
Reemergence of Pertussis in the Highly Vaccinated Population of The Netherlands: Observations on Surveillance Data
Table 2
Reported cases according to vaccination status and estimate of vaccine-effectiveness according to method of diagnosis
1- to 4- yr-olds | Vaccine efficacy | 5- to 9- yr-olds | Vaccine efficacy | ||
---|---|---|---|---|---|
Year | Method of diagnosis | (N) | (%)a | (N) | (%)a |
1993 | Microbiologic | 14 | 93 | 14 | 94 |
2-point serology | 25 | 91 | 28 | 75 | |
1-point serology | 24 | 79 | 26 | 50 | |
Otherb | 35 | 96 | 20 | 90 | |
Total | 98 | 93 | 88 | 84 | |
1994 | Microbiologic | 23 | 56 | 15 | 42 |
2-point serology | 36 | 67 | 36 | 83 | |
1-point serology | 63 | 71 | 65 | c | |
Otherb | 37 | 89 | 29 | 91 | |
Total | 159 | 77 | 145 | 72 | |
1995 | Microbiologic | 14 | 85 | 9 | 67 |
2-point serology | 27 | 82 | 19 | 64 | |
1-point serology | 39 | 64 | 45 | c | |
Otherb | 37 | 53 | 27 | 67 | |
Total | 117 | 72 | 100 | 45 | |
1996 | Microbiologic | 116 | 67 | 123 | 3 |
2-point serology | 245 | c | 288 | 49 | |
1-point serology | 545 | c | 782 | c | |
Otherb | 290 | 66 | 355 | 40 | |
Total | 1196 | 34 | 1548 | 16 | |
1997 | Microbiologic | 63 | 51 | 68 | 57 |
2-point serology | 110 | c | 131 | c | |
1-point serology | 283 | c | 345 | c | |
Otherb | 244 | c | 260 | c | |
Total | 700 | c | 804 | c |
aEstimated vaccine effectiveness; a vaccine-coverage of 96% was used to estimate the incidence and vaccine effectiveness.
bEpidemiologic, serologic (differentiation between positive two-point serology and positive one-point serology not possible), clinical or method of diagnosis unknown.
c Vaccine effectiveness could not be estimated as the percentage vaccinated was more than 96%.
1Vaccine effectiveness = 1 – (proportion of vaccinated cases/1 – proportion of vaccinated cases) X (1 – proportion vaccinated in the population/proportion vaccinated in the population).